Chapter 5.5, Problem 7E

Let $\left\{u_1,u_2,u_3\right\}$ beanorthonormalbasisforaninner product space V. If $x=c_1{u}_1+c_2{u}_2+c_3{u}_3$ is a vector with the properties $\Vert x\Vert =5,\langle u_1,x\rangle =4,$ and $x\perp u_2,$ then what are the possible values of $c_1,c_2,c_3?$