Two rods, one of aluminum and the other made of steel, having initial length l1 and l2 are connected together to form a single rod of length l1+l2. The coefficients of linear expansion for aluminum and steel are αa and αs respectively. If the length of each rod increases by the same amount when their temperature are raised by t∘C, then find the ratio l1/(l1+l2).
a. αs/αa
b. αa/αs
c. αs/(αa+αs)
d. αa/(αa+αs)