The answer is 121. Why?

Frances and Francis trade between themselves. Frances's utility function is u(x,y)=x+154y1/2. Francis's utility function is u(x,y)=x+7y. At a Pareto optimal allocation in which both individuals consume a positive quantity of each good, how much y does Frances consume? 9 22 18 121 It is not possible to answer this question without information on the total quantity of both goods