15. Refer to the curve shown below. (a) Sketch the lines tangent to the curve at x = 1, 2, 3, 4 and 5. (b) For what value(s) of x is the value of the func- tion largest? Smallest? (c) For what value(s) of x is the slope of the tan- gent line largest? Smallest? 3 2+ - - 2 3 4