Let D be an n × n matrix for a Leontief input-output model. We will say this models an economy with n industries I1, I2, · · · , In. Let x be an n × 1 vector. 1. Consider two possible conditions: (R) The entries of row k sum to 1: Sigma from j=1 to n Dkj=1 (C) The entries of column k sum to 1: Sigma from k=1 to n Dik=1 Both of these conditions can be interpreted in economic terms for input-output models. Briefly (but meaningfully) explain.