The data frame WCG contains data from a study started in 1960 about heart disease. The study used 3154 adult men, all free of heart disease at the start, and eight and a half years later it recorded into variable chd whether they suffered from heart disease (1 if the respective man did and 0 otherwise) along with their height and average number of cigarettes smoked per day. Consider the $\mathrm{R}$ code below and its abbreviated output.

(a) Write down the model fitted by the code above.

(b) Interpret the effect on heart disease of a man smoking an average of two packs of cigarettes per day if each pack contains 20 cigarettes.

(c) Give an alternative latent logistic-variable representation of the model. [Hint: if $F$ is the cumulative distribution function of a logistic random variable, its inverse function is the logit function.]