What is the formula for A.P.I. degrees used in gravity tests for fuels?

(a) A.P.I. degrees = \(\frac{141.5}{specific \, gravity \, of \, oil \, at \, 60°F} \)-131.5

(b) A.P.I. degrees = \(\frac{131.5}{specific \, gravity \, of \, oil \, at \, 60°F} \)-141.5

(c) A.P.I. degrees = \(\frac{Specific \, gravity \, of \, oil \, at \, 60°F}{141.5} \)-131.5

(d) A.P.I. degrees = \(\frac{Specific \, gravity \, of \, oil \, at \, 60°F}{131.5} \)-141.5

This question was addressed to me in examination.

My question is taken from Fuel Supply System topic in portion Fuel Supply and Cooling System of Farm Machinery