Essential University Physics: Volume 1 (4th Edition)

b) $5.5 \ km/s$
We use the equation for escape speed to find: $V_{esc} =\sqrt{\frac{2GM}{r}}$ $V_{esc} =\sqrt{\frac{2(6.67\times10^{-11})(5.97\times10^{24})}{6.37\times10^6+(20.2\times10^6)}}=5470\ m/s = 5.5 \ km/s$