Suppose dA/dt=k(100-A), where k > 0 is a constant and A < 100. Of A = A0 when t = 0, then

Jada has a meal in a restaurant she adds up the prices listed on the menu for everything they ordered and gets a subtotal of $42.00. when the check comes, it says they also need to pay $3.99 in sales tax. what percentage of the subtotal is the sales tax