At time 0, $100 is deposited into find x and also into fund y. Fund x accumulates at a force of interest st=0.5(1 t)⁻²$. What is the value of x at time t?
a) $100e0.5t²$
b) $100e-0.5t²$
c) $100e-0.5t$
d) $100e0.5t$