In England, the tax on soft drinks was recently introduced. Australians buy 1.29 billion litres of sugar-sweetened drink

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In England, the tax on soft drinks was recently introduced.
Australians buy 1.29 billion litres of sugar-sweetened drinks per
annum. Currently, the average price of these drinks is $1.7/litre.
Assume that government wants to implement a sales tax (x% per
litre) on soft drinks to reduce their sales (or demand) to 700
million litres. The price elasticity of demand for soft drinks is
-0.89.
a) How much sales tax should be imposed to achieve the demand
target of 700 million litres? Hint: Find the value of x.
b) How much additional revenue will be raised by this tax?