The marginal, average and total product curves encountered by the firm producing in the short-run exhibit all of the following relationships except:
(a) when total product is rising, average and marginal product may be either rising or falling
(b) when marginal product is negative, total product and average product are falling
(c) when average product is at a maximum, marginal product equals average product, and total product is rising
(d) when marginal product is at a maximum, average product equals marginal product, and total product is rising
