The current spot exchange rate is USD$0\mathrm{.}7/$AUD$.$ Which of the following statements is correct?

a$.$ If USD's value decreased by $10\%$ against the AUD, the new exchange rate would be USD$0\mathrm{.}63/$AUD$.$

b$.$ If Relative Purchasing Power Parity holds, and the expected inflation rates in the US and in Australia are $5\%$ and $10\%,$ the exchange should change to USD$0\mathrm{.}7333/$AUD$.$

c$.$ If Absolute Purchasing Power Parity holds and price index in the US is USD$140,$ then price index in Australia should be AUD$200.$

d$.$ If the economic uncertainty increases in the US but not in Australia, the AUD would depreciate against USD.

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