Maria has a business designing and making custom T-shirts. Her cost for materials, in thousands of dollars, is given by M (t) = -3t² + 36t, where t is the number of the month (1-12) on the last day of the month. Her income from sales is given by S(t) = -4t? +48t. What is the
function P (t) that gives her profit as a function of time?