When I was in graduate school, I shared an apartment with a fellow who was madly in love with a woman who lived in another city. They agreed to split the costs of their long-distance phone calls...

When I was in graduate school, I shared an apartment with a fellow who was madly in love with a woman who lived in another city. They agreed to split the costs of their long-distance phone calls equally, regardless of who placed the calls. (In those days, long-distance calls were expensive and billed separately from general phone service.) What was the implication of this fee-sharing arrangement on their total phone bill? Why?