Statspotting

A friend shared a stat in the news

The Guardian

Our place in the sun: Australia’s uptake of solar panels is already through the roof. How much higher could it get?

the capacity of rooftop solar systems will grow from its current level of 20GW to 87GW by 2050

It's in today's paper. How big is it? Four answers, and your first pick has to be right to spot it.