How many arrows would an archer fire in a battle, how does this compare to early infantry wielded firearms?

According to Juliet Barker in her study of the Battle of Agincourt:

“A Welsh or English military archer during the 14th and 15th Century was expected to shoot at least ten ‘aimed shots’ per minute. An experienced military longbowman was expected to shoot twenty aimed shots per minute. A typical military longbow archer would be provided with between 60 and 72 arrows at the time of battle, which would last the archer from three to six minutes, at full rate of fire. Young boys were often employed to run additional arrows to longbow archers while in their positions on the battlefield.[8]”

By contrast, the matchlock arquebus introduced in the late 15th century took 30-60 seconds to reload, allowing for a rate of fire of perhaps one or two shots a minute. The muskets of the 18th and 19th century were faster, but even the best crack infantry regiments of the British army could only manage 5 shots a minute. 

The reason why the firearm replaced the bow is partly because the noise and smoke and stopping power of bullets was quite frightening on the battlefield, but mostly because it was much faster to train someone to use a musket than to use a bow, and because expensive firearms required storage in a central depot to keep them maintained, making them more suited to centralized standing armies.