A potential offer by Verizon (VZ) for Vodafone's stake in their US wireless joint venture would have to increase substantially to please the British telecom group's shareholders, according to Jefferies.Jefferies said: "The glaring issue raised by last night's [Reuters] article is of course price. $100bn is nowhere close to the level at which Vodafone can consider a deal, even assuming a minimal capital gains tax charge. The Sunday Times article on March 24th floated a valuation for the VZW stake of $135bn (and this before estimate upgrades that followed last week's VZ first-quarter results).""The valuation will need to climb to much higher to create an outcome acceptable to VOD shareholders in our view."First-quarter results from AstraZeneca were broadly in line with forecasts with the stock is up with events after a good run of late, according to Panmure Gordon."Overall we have been advocating taking profits in recent weeks whilst the share price defies gravity. These results were not likely to change anyone's stance on the stock, with bigger challenges further down the line," Neophytou said.Shares of Admiral may be expensive but worth a 'buy', according to Bank of America Merrill Lynch (BofA) following the car insurer's first-quarter results on Thursday.The stock trades at 12.8 times 2014 earnings, a "rich multiple" compared to the sector, the broker said. "We believe this is justified due to: 1) the high quality insurance operations; 2) over 50% of earnings arising from higher quality, high margin fee income; 3) a debt free balance sheet. BC