As John was leaving the show, he was unable to hear his friend talking next to him in a normal conversational tone of decibels since the rock concert was well over 130 decibels.

60 decibels

Explanation:

Human Hearing depends on sound which is measured in decibels. A very loud sound can cause severe damage or temporary deafness to the ear. A normal human conversation level is about 60 decibels. A higher frequency of noice than this could cause cause the ear not to hear at the normal rate of 60 decibels

b) trade is easy because of the direct line between their major ports. bilateral trade reached 89,6 thousand million.