Apharmacy wants to survey its customers to find out which brand of toothpaste they prefer.

which survey methods are likely to be biased?

One hundred people from the pharmacy’s customer list are selected at random, called on the phone, and asked.  
or 
Those customers who buy toothpaste with a coupon are selected, and the toothpaste brand they purchased is recorded.

My discoed name is puking little kid

The density of the cube is 40