A woman operating her own business is trying to plan her weekly sales activity schedule to produce the most valuable sales results in the least possible time. She can make personal visits, do phone calls, or work on mass mailings. She estimates that each hour spent on personal visits nets her \(\$ 50\), each hour on phone calls earns \(\$ 40\), and each hour on mass mailings earns \(\$ 20\). To limit her transportation and phone costs, and to reach a wider audience, she will spend at least twice as much time on the phone as she spends making personal visits, and at least twice as much time doing mass mailings as she spends making phone calls. If her goal is to make at least \(\$ 1000\) per week, how should she allocate her time so as to spend as few hours as possible?