c
\(i G=(I-i) S\) where \(G\) is the galvanometer resistance and \(S\) is the shunt used with the ammeter. \(1.0 \times 60=(5-1) S\) where \(S\) is the shunt used to read a \(5\, A\) current when the galvanometer can stand by \(1\, \mathrm{A}.\)

\(S=\frac{1.0 \times 60}{4}=15 \,\Omega \) in parallel.