The crazy carmel corn company has determined that the percentage of kernels that pop rises and then falls as the temperature of the oil the kernels are cooked in increases. It modeled this trend using the equation p=-1/250t² + 2.8t - 394. What is the maximum percentage of kernels that pop?
a) 2.8%
b) 394%
c) 250%
d) 394.5%