Where a taxing provision specifies a precise arithmetical formula for calculating tax liability and obliges an assessor to 'determine' the amount payable, the assessor is bound to apply the formula and has no discretion to adjust the result, even if the literal application produces results that might be considered unfair. The phrase 'calculated in accordance with the following formula' requires strict application of the formula. A court should not attribute to Parliament an intention to confer a discretion where the putative discretion would itself operate in an arbitrary and irrational fashion.
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