Helpers, Inc., a qualifying § 501(c)(3) organization, incurs lobbying expenditures of $250,000 for the taxable year and grass roots expenditures of $0. Exempt purpose expenditures for the taxable year are $1,200,000. Helpers elects to be eligible to make lobbying expenditures on a limited basis. 

a. What amount of lobbying expenditures is Helpers allowed to make tax-free under the terms of the election? 

b. What is its tax liability as a result of the election?

c. Express your answer to part (b) as a Microsoft Excel formula.