A consumer's utility function for goods $1$ and $2is$ given $by$

$U(x1,x2)=(x1+x_2)x_2.$ Assume the existence $of$ two other goods, $3$ and $4.$ Suppose each

unit $of$ good $3$ provides $1$ unit $of$ good $2$ and $1$ unit $of$ good $1,$ while $1$ unit

$of$ good $4$ provides $1$ unit $of$ good $1$ and $0$ units $of$ good $2.$ Determine his

utility function $in$ terms $of$ goods $3$ and $4.$