1 fathom = 6 feet = 2 yards
It is a known (by everyone in the trade but not admitted by the nice people at B & S - as far as I know) fault in that modern fuel eats through the carburetta diaphragm within 12 to 18 months. It is a 15 minute task to replce and a $5 part. They do not make a more durable diaphragm, sadly. Aparently modern fuel additives damage the rubber.
There is no diaphragm on your 18 hp Briggs. Only small lawn mowers with the fuel tank mounted to the bottom of the carburetor use a diaphragm. It is likely that the idle circuit is has some debris in it as well as the main jet. You should use Stabil gas stabilizer or Marvel Mystery Oil in all fuel used for small engines to prevent future problems. To correct the problem, go to your local automotive store such as autozone and purchase a 16 oz. can of SeaFoam. Mix 4 oz of SeaFoam to 1/2 gallon of gas...so if you feel like you have a couple gallons in the tank, pour about half the can of SeaFoam in and shake the tractor around to mix. The machine should run much better after running an hour or two. If this fails you will need to remove and disassemble the carburetor and clean throughly with carburetor cleaner, spraying trough every orifice you can find
What makes this question tricky to answer is the understanding of the terms. Were the correct terms used in the question, and does the question poster and answer contributor have the same understanding of those terms? Having said that, here goes. A prism is a polyhedron with at least two congruent parallel faces. They are called the bases. The other faces (the "lateral faces") are parallelograms that are formed by lines that connect the corresponding vertices of the two bases. A quadrangular prism has a quadrangular base (such as a rectangle). If the base is some sort of regular polygon, it's called a regular prism. The lateral area of a prism is defined as the total area of the lateral faces. To calculate the lateral area, you multiply the length of an edge by the perimeter of the face that is perpendicular (at right angles to) to that edge. So, assuming the height, 4 cm in this case, is perpendicular to the perimeter, 16 cm, we calculate the lateral area to be 4 x 16 or 64 square centimeters or 64 cm2.
There are a couple of factors. One is the rotation of the earth. Travelling west and the destination is moving toward you. Travel east and it is moving away from you. Another is the winds that affect flight.
Most women ovulate 12-17 days after the first day of their last menses (average 14), the most fertile days are the three days prior to ovulation. The ovum (egg) remains viable for 12-24 hours, and the sperm remains viable for approx. 72 hours. Intercourse on any of these three days will produce approx. a 20% chance of pregnancy if both partners are normal and healthy.