Could some please point me in the right direction for the question below: -

"For the summing amplifier, obtain values of R1, R2, R3 and Rf that achieve the following output Vo. Assume that the minimum input resistance is 30 kΩ. Show the formulas used and all working out. = −[51 + 22 + 3]"

Am correct in thinking Rf is either 150Kohms or 60KOhms? I can then use V

*o*= -(rf/r1*V1 + rf/r2*V2 + Rf/r3*V3) to calculate for r1, r2, r3.

Any help would be greatly appreciated, kind regards