I bought it for/at 90 yuan.请问,for和at都可以吗?

I bought it for/at 90 yuan.请问,for和at都可以吗? i bought it at the shopping mall. I bought a computer for ___.I often use it. I bought a computer for ___.I often use it. When have you bought the book?Two weeks ago.I have bought it for two weeks. 1.Please wait for me at the ferry t___.I will be there soon.2.The r___ why I bought this sweater was that it was so cheap. the recorder ( )has gone out of order.A.I borrow it for her B.which I bought it for her C.I bought for her D.what I bought for her I bought a book for it's such an interesting book.i have bought it for two years错误的地方 I bought my car in 2005 ,and so I () it for 4 years.(have) I bought a new kite for you .I'll give you it tomorrow.哪里有错?非诚勿扰 i bought the redio ___ the price of 100 yuan.填at 还是for i bought a sweater for you .please put it on 这句话是什么时态 Andy,look at what we bought for you in the shop.It is a model ship!Rea The coat bought last week is too big for me .I'd like to change it for a _smaller____one对吗? simon's family gave it to me.为什么用to,I bought these for my friends.为什么用for? I bought a shirt for you .Please try it _____.A in B for C with D on ( )19.She has a very nice watch.She said she bought it _____only 10 yuan.A.for B.at C.with D.选哪个 at还是 for?