It would be 1.55x10 to the 9th
hope that helps you
Answer: c. +4
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.




Here manganese is having an oxidation state of +4 called as cation and oxygen forms an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged to give
which written in simplest whole number ratios to give neutral 
PH stands for "Potential Hydrogen" and the PH scale ranges from 0-14. PH refers to the ability to attract hydrogen ions.
The PH of a solution either indicates acidity of the solution or alkalinity of the solution. A solution which has PH 7 above is a base solution where a solution with PH less than 7 is an acidic solution.