The midpoints formula is an approximation, which is also called the arc elasticity. When the function of the demand curve is known, instead of the arc elasticity, we can calculate the point elasticity. The formula of point elasticity is E = (1/slope)(P/Q). If a demand curve is P = 100 - 2Q, then which of the following is true?
A. When Q = 10, |E| = 8.
B. When Q = 10, |E| = 4.
C. When Q = 25, |E| = 1.
D. Only A and C.
E. Only B and C.