Gold and silver rebounded in New York after the Federal Reserve unexpectedly reduced its discount rate, sending the dollar lower and increasing the investment allure of precious metals. The Fed said it is prepared to take further action to “mitigate” damage from the rout in credit markets. Commodities yesterday plunged the most in at least five decades as crashing equities led investors to sell metals, energy and grains to raise cash. Gold often moves in the opposite direction of the dollar, which fell as much as 0.9 percent versus the euro today.