2. Solve the equations written here for the indicated vari- able: (a) y = 2e" 2; for r. (b) y = 2e" 4; for x. (c) 2 = loge (a(x - b)); for a and then 2. (d) N = Noe-:t for t. This is the equation for radioactive decay, where N is the number of atoms of an element and is a parameter for that element. (e) In the previous equation, right down an equation linking the parameter 1 and the half-life, the time it takes the number of atoms to drop by one-half