How much do U.S post Service charge for an EMS/EMIS package to Ghana?

I would like to know how much the U.S post service would charge me for a 0.57 kg letter am sending to my pal in Ghana if it would take like 5-6 days?|||Half a kilo ? It's almost $1 an ounce now to send something over seas. It's going to be at least $16+. And you won't know how long it will take. I mail things to Japan all the time. And it can take from three days up to nine to get there.