Given: r ∥ s Prove: m r = m s Two parallel lines passing the vertices with red line r at points (c, d) at (2, 10) and (0, b) at (0, 6) and blue line s intercepts (c, 0) at (2, 0) and (0, a) at (0, minus 4) Statements Reasons 1. r ∥ s given 2. m r = d − b c − 0 = d − b c m s = 0 − a c − 0 = - a c application of the slope formula 3. distance from ( 0 , b ) to ( 0 , a ) equals the distance from ( c , d ) to ( c , 0 ) definition of parallel lines 4. d − 0 = b − a application of the distance formula 5. m r = ( b − a ) − b c substitution property of equality 6. m r = a c inverse property of addition 7. m r = m s substitution property of equality Which step of the proof contains an error? A. Step 6 B. Step 2 C. Step 5 D. Step 4