In the small closed economy of San Lucretia, the currency is the denar. Statistics for last year show that private saving was 60 billion denars, taxes were 70 billion denars, government purchases of goods and services were 60 billion denars, there were no transfer payments by the government, and GDP was 400 billion denars. What was investment in San Lucretia?

a.70 billion denars

b.80 billion denars

c.50 billion denars

d.60 billion denars