Tax base - development costs

Dear all, Could you please help me to understand the following: 1. Why is the tax base 0? I'm reading the answer, but i still don't get it... 2. Why is it a deferred tax liability, and not deferred tax asset? Activity 3: Epsilon Co During the year ended 31 March 20X4, Epsilon Co correctly capitalised development costs of $1.6 million in accordance with IAS 38. The development project began to generate economic benefits for Epsilon from 1 January 20X4. The directors of Epsilon Co estimated that the project would generate economic benefits for five years from that date. Amortisation is charged on a monthly pro-rata basis. The development expenditure was fully deductible against taxable profits for the year ended 31 March 20X4 and the rate of tax applicable is 25%. Required Discuss the deferred tax implications of the above in the financial statements of Epsilon for the year ended 31 March 20X4. Answer: ".... The tax base of the development costs is nil since the relevant tax deduction has already been claimed. The deferred tax liability will be $380,000 ($1.52m × 25%)."