A new mixture of​ self-tanning & moisturizing lotions for everyday use is being developed. This mixture is made by mixing 900 ounces of everyday moisturizing lotion for ​$0.90 per ounce with​ self-tanning lotion worth ​$33 per ounce. If the new​ self-tanning & moisturizing lotion mixture is to cost $1.60 per​ ounce, how many ounces of the​ self-tanning lotion should be in the​ mixture?