Complete the following sentence: Walker was given a full-time Formula One seat to drive the Lotus 72 in the 1972 season, as number two driver to Emerson Fittipaldi. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ After Lotus discovered Walker had tested a Formula Two car for another team, he was dropped from the team for the
️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ Walker was back for the US GP, but retired.<unk> Walker was back for the US GP, but retired.<unk>