In a copper voltmeter, mass deposite in `30` seconds is `'m'` gram. If the time-current graph is as shown in figure. `ECE` of copper is

Explanation

Using `Z=(m)/("lt")` (m is mass deposited at the end of 30s)
where it=Areas OABC of graph `=2xx(1)/(2)xx10xx0.1+10xx0.1=2C`
Then, `Z=(m)/(2)gC^(-1)`