Which of the following would be a possible solution to the differential equation that models the following verbal statement: The rate of change of ( q ) with respect to ( x ) is proportional to ( 40 - q )?

a) ( q(x) = 40 - Ce⁻kx )
b) ( q(x) = 40 + Ce⁻kx )
c) ( q(x) = 40 - Ceᵏx )
d) ( q(x) = 40 + Ceᵏx )