Suppose that 4 J of work is needed to stretch a spring from its natural length of 34 cm to a length of 43 cm. (a) How much work (in J) is needed to stretch the spring from 36 cm to 38 cm? (Round your answer to two decimal places.) :1 (b) How far beyond its natural length (in cm) will a force of 10 N keep the spring stretched? (Round your answer one decimal place.) :cm