Kiersten runs a website that helps people learn programming. Every month, Kiersten receives a subscription fee of $10 from each of the subscribers to her website. Last month, the website had 100 subscribers. This month, 30 new members joined the website, and 10 members cancelled their subscription.
How much money will Kiersten’s online business earn this month?

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?