The equation to the normal to the curve $y^4=ax^3$ at $(a,a)$ is

Question

$$\begin {array} {1 1} (1)\;x+2y=3a & \quad (2)\;3x-4y+a=0 \\ (3)\;4x+3y=7a & \quad (4)\;4x-3y=3 \end {array}$$