give the output Vo = 8(V4) + 4(V3) + 2(V2) + V1.

(a)

Sketch a suitable op-amp circuit to give the required output and show

the required resistor ratios.

Vo=8(V4)+4(V3)+2(V2)+V1. I need to design an Op Amp circuit and provide the required resistor ratio values using the "Vo" equation. I know it is a summing amplifier circuit required and the amplification factor, in case of V4 for example is 8. I know that amplification factor is equal to -Rf(feedback resistor) divided by R1,R2 etc (-Rf/R.) If i can find Rf then the rest is easy, any ideas?

This my design. Rf being R5 in the picture below