There will be three pairs of matching sides: one pair 5x7, one pair 5x12 and one pair 12x7. We can compute the are of each side (in pairs) and then add up the total:
\(A_{surf}=2\times(l \times w)+2\times(l \times h)+2\times(h \times w)\)
\(A_{surf}=2\times(5\times7)+2\times(5\times12)+2\times(12\times7)\)
\(A_{surf}=2\times35+2\times60+2\times84\)
\(A_{surf}=70+120+168\)
\(A_{surf}=358\)
\(A_{surf}=358m^{2}\)
