Joyce Reid Troost Architecture is doing a review of their marketing budget and efficiency. As they begin reviewing they learn that internet marketing costs $20 per directory and the last directory produced 0.2 sales calls. The company pays $120 per newspaper advertisement and the last advertisement produced 0.4 sales calls. Finally, they bought space at the Nanaimo Home Display Convention at the cost of $500 per table and it led to 5 sales calls. What would you recommend to improve marketing efficiency? Explain using math and words.