After Federal Trade Commission and Department Justice required CPA firms to compete with each other in $1979,$ which of the following strategies was the most popular and profitable among CPA firms between $1980$s and early $2000$s$?$

After Federal Trade Commission and Department Justice required CPA firms to compete with each other in $1979,$ which of the following strategies was the most popular and profitable among CPA firms between $1980$s and early $2000$s$?$

Improve service quality through employee training

Cut auditing costs through hiring more interns and junior associates

Increase realization rate

Sell consulting service to audit clients