Radioactive substances A and B have decay constants of 0.02 and 0.05, respectively. If a mixture of these two substances at time t=0 contains MA grams of A and Mg grams of B, then a model for the total ame of the mixture present at time t is y = Mae -0.02t + Mge -0.05t Suppose the initial amounts Ma and Me are unknown, but a scientist is able to measure the total amount present at several times and records the following points (t, y,) : (10, 21.38), (11, 20.69), (12, 20.02),. (14, 18.82), and (15, 18.34). a. Describe a linear model that can be used to estimate M, and Ma. b. Find the least-squares curve based on the equation y = M,e -0.02t + Mee -0.05t -0.02(10) e -0.05(10) 21.38 e -0.02(11) -0.05(11) e E2 20.69 MA e= E3 Ma X= -0.02(12) -0.05(12) ,y = 20.02 -0.02(14) -0.05(14) 18.82 €4 18.34 e -0.02(15) -0.05(15) e (Type exact answers.) b. The least-squares curve is given by the function y= De -0021 + ( De -0.05t (Round the final answers to two decimal places as needed. Round all intermediate values to four decimal places as needed.)