Function. Plants also have a pH rating. Plants whose pH matches the soil's pH can take up nutrients more efficiently than plants with a pH rating different than the soil. Pine trees and the needles that they produce prefer acidic soil.
Price of a Stamp. The current price of a first class stamp is 49 cents. A domestic first class letter (1 oz.) is 49 cents. The price of each additional ounce is 21 cents. It will cost you 34 cents to send a domestic postcard.
Re: Using stamps - getting the amount correct with new stamps? The Forever stamp is always going to be worth whatever the current postage rate for 1 ounce is. So even you bought it for 46 cents it is now worth 49 cents of postage. I always have a small supply of add on stamps that I can attach for oversize, overweight, second ounce, etc. letters.