4. Alphabet Inc., the parent company of Google, disclosed the following financial figures for the fiscal year ending December 31, 20XX:
   • Total assets: $900 billion
   • Current assets: $300 billion
   • Non-current assets: $600 billion
   • Total liabilities: $400 billion
   • Current liabilities: $150 billion
   • Non-current liabilities: $250 billion

Compute the subsequent ratios for Alphabet Inc.:

a) Current ratio b) Debt-to-total-assets ratio c) Working capital d) Quick ratio