EXERCISE 3.68. Let S be an orientable regular surface and let N be an orientation for S. Let 6:S + R be a smooth function. Assume that has compact support, which means that there exists a compact subset K CS such that y equals zero at every point of S K. For t e R, define St = {p+ty(p)N(p) [PES}. Prove that for sufficiently small t, St is a regular surface. EXERCISE 3.68. Let S be an orientable regular surface and let N be an orientation for S. Let 6:S + R be a smooth function. Assume that has compact support, which means that there exists a compact subset K CS such that y equals zero at every point of S K. For t e R, define St = {p+ty(p)N(p) [PES}. Prove that for sufficiently small t, St is a regular surface