The Mean Value Theorem is one of the most important theoretical tools in Calculus. It states that if f(x) is defined and continuous on the interval [a,b] and differentiable on (a,b), then there is at least one number c in the interval (a,b) (that is a < c < b) such that
f'(c) = ( f(b) - f(a) ) / b - a= 642 - 42 / 1.5 h= 400 mphso the answer B