U.S. stocks added to gains in the final hour of trading on Friday even as Fed Chair Janet Yellen suggested the central bank could implement another rate hike this summer. Yellen's comments coalesce with the past two weeks of increased Fed talk. Verizon (VZ - Get Report) rose after reaching a 'tentative agreement' with two unions which will end a six-week strike. The strike, the largest in five years, involved roughly 37,000 workers. LendingClub (LC - Get Report)  shares soared on reports it has entered discussions with Citigroup (C - Get Report) about buying or financing future loans. The discussions are part of the peer-to-peer lender's efforts to calm existing investors as it undergoes an investigation into some of its loans. Vivint Solar (VSLR - Get Report) rocketed higher after analysts at Deutsche Bank upgraded the stock to BUY. TheStreet's Keris Lahiff reports from Wall Street.