Given the equation P = (R(T)/(v-b)) - (a)/(v^(2)), where P is the pressure in pascal, v is the volume of steam in m^3, T = 623.15K, and R Specific Gas Constant = 0.46189 kJoule/(kg*K), find the value of the first derivative of P with respect to v.
a) -RT/(v-b)^2 + 2a/v^3
b) -RT/(v-b)^2 - 2a/v^3
c) RT/(v-b)^2 + 2a/v^3
d) RT/(v-b)^2 - 2a/v^3