Pls answer quickly
A teacher received the following answer to a quiz question in which the student was asked to simplify the expression in Step 1:

Step 1: −3(x − 14y) + 6(−3x − 5y)
Step 2: −3x + 42y − 18x − 30y
Step 3: −3x + 18x + 42y − 30y
Step 4: (−3x + 18x) + (42y − 30y)
Step 5: 15x + 12y

Part A: Identify the step where the student made a mistake and explain the specific error that was made. Support your answer using the correct vocabulary. (6 points)

Part B: How would you correct the mistake? Show all your work. (6 points)