The rupee plunged by 42-paise to settle at a one-and-a-half-month low of 71.80 against the US-currency due to a spike in crude oil prices after US-President Donald Trump ordered the killing of a top Iranian general. General Soleimani, the head of Iran's elite al-Quds force and architect of its regional security apparatus, was killed following a US airstrike at Baghdad's international airport on Friday.