How does overall national savings relate to overall investment and why savings is always equal to investment?

How would changes in interest rates affect the amount of money that people save?

How would changes in interest rates and rates of return on various investment options affect the amount of money that businesses are willing to invest to increase output?

How would government tax revenue and government spending create either a budget surplus or budget deficit? How does that difference affect the market for loanable funds?

From these tow formulas

Y = C + I + G + EX - IM

S = (Y - T - C) + (T - G)

Identify the components of each formula. What is the relationship between the two formulas.