Identify a and b, isomers of molecular formula c3h4cl2, from the given 1h nmr data: compound a exhibits peaks at 1.75 (doublet, 3 h, j = 6.9 hz) and 5.89 (quartet, 1 h, j = 6.9 hz) ppm. compound b exhibits peaks at 4.16 (singlet, 2 h), 5.42 (doublet, 1 h, j = 1.9 hz), and 5.59 (doublet, 1 h, j = 1.9 hz) ppm.