If y=f(x) and dxdyx=a=7, what does the value 7 represent?
a) Rate of change of x with respect to y at x=a
b) Average rate of change of y with respect to x over the interval [a,a+1]
c) Slope of the tangent to the curve y=f(x) at x=a
d) Area under the curve y=f(x) from x=0 to x=a