Grailroad tracks are made from segments l = 79 m long at t = 20° c. when the tracks are laid, the engineers leave gaps of width l between adjacent segments to allow for thermal expansion. the coefficient of linear expansion is α = 12 × 10-6 °c-1 and engineers design the tracks to withstand temperatures of tc = 39.5 degrees.

(a) enter an expression, in terms of given variables, for the minimum gap distance l the engineers must leave for a track rated at temperature tc