ans is 16 percent

let T eqals = -t^2/6+4*t+12 ( where t is elapsed time)

rate of change in temp. eqals dT/dt

dat is -4t^2-36t/(18+4*T)^2

here time elapsed is 3

putting the value t eqal 3

we get 144/900

so percentade change

(144/900)*100

ans 16 percent