0.4×1.7×2+0.2×1.7×2+0.2×0.4+0.2,
=0.68×2+0.34×2+0.08+0.2,
=1.36+0.68+0.08+0.2
=2.32(平方米);
答:做这只套子至少需用2.32平方米的布.