Constrained optimisation with transfer
I'll guess that, since you're not yet in college but you're doing something this "advanced," you're not doing a homework problem, and that you're asking for a hint.

Since B doesn't care about A, you should be able to find B's consumption $(C_B, l_B)$ using standard method (maximizing utility w.r.t. budget constraint, etc.)

Now there are two cases.


$C_B \geq 1$. Then what would the problem for A turn out to be?
$C_B &lt; 1$. Then think about how much should A transfer to B? Should he transfer nothing? 0.1? Up until what point would the increase in the transfer stop making A better off?